This invention relates to an audio system and, more particularly, to an improved sound motion picture system.
One problem associated with audio systems which utilize relative motion between an audio recording medium, such as a magnetic tape, and an audio transducer is frequency modulation resulting from relative motion between components of the system and particularly from speed variations of the recording medium. This problem is particularly evident in tape systems wherein the flexibility of the recording medium contributes to a lack of consistent transducer engagement and constant linear velocity of the medium so as to produce both audio flutter and drift.
In high fidelity equipment, flutter and drift are generally reduced by complex audio-drive mechanisms in conjunction with corrective electronics which significantly increase the cost and size of this equipment and require maintenance of, and precise adjustment of, the components such that they are not well suited to high quality, mass produced, portable devices. Additionally, these problems are further complicated when the audio system is combined with visual reproduction, such as in audio-visual systems wherein the audio portion of the system requires constant tape velocity and the motion picture generally utilizes intermittent motion.
The use of a vacuum for high speed magnetic tape systems to either support the tape for transducer engagement or for driving the tape is known as, for example, in high speed vidio equipment as described in the book "Magnetic Recording" authored by Charles E. Lowman and published in 1972 by McGraw-Hill, Inc. For instance, page 42, FIGS. 5-9 of this book illustrates a magnetic tape recording system wherein a vacuum guide is employed to support the tape beneath the transducer head. Furthermore, on page 97, FIGS. 8-3 and page 237, FIGS. 12-16 thereof, vacuum capstans are illustrated. These systems are, of course, relatively costly and complex arrangements which, while suited to high speed tape equipment, do not particularly alleviate the difficulties of cost, portability and construction noted above.
Consequently, it is an object of this invention to provide a highly efficient audio tape system having reduced tape instability.
A further object is to provide a compact audio system having minimum flutter.
Another object is to provide an audio-visual system having reduced audio tape instability.
Still another object of this invention is to provide a compact audio tape drive and recording system suitable for use with audio-visual cassettes.
A still further object is to provide an improved audio tape system employing vacuum produced forces.